Monday, April 5, 2010

March 2010 SST Anomaly Update

The map of Global OI.v2 SST anomalies for March 2010 downloaded from the NOMADS website is shown below. Note the pattern of warm SST anomalies over the Southern part of the North Atlantic and cool SST anomalies in the Gulf of Mexico. If the pattern persisted through the summer months (big IF), how would it impact the hurricane season?

http://i42.tinypic.com/rur969.png
March 2010 SST Anomalies Map (Global SST Anomaly = +0.301 deg C)
Note: I was advised via email that the NOAA corrected the February OI.v2 SST data. It represents an upward change of only ~0.005 deg C globally, but since it was a correction in areas with sea ice, I decided to check those as well. The February Arctic Ocean SST anomalies rose ~0.02 deg C and the Southern Ocean SST anomalies ~0.03 deg C with the corrections.MONTHLY OVERVIEW

There was a minor rise (0.012 deg C) this month in Global SST anomalies. SST Anomalies in both the Southern and Northern Hemispheres rose approximately the same amount. El Nino conditions remain in the central tropical Pacific (Monthly NINO3.4 SST Anomaly = +1.14 deg C and Weekly NINO3.4 SST Anomaly = +0.97 deg C), but SST anomalies there are dropping. Monthly NINO3.4 SST anomalies dropped 0.10 in March. The North Atlantic, Indian Ocean and the East Indian-West Pacific Ocean datasets all show significant rises this month. They are partly offset by the drops in the Pacific and South Atlantic.http://i40.tinypic.com/4rav48.png
Global
Monthly Change = +0.012 deg C
############http://i44.tinypic.com/24yvcrt.png
NINO3.4 SST Anomaly
Monthly Change = -0.104 deg C
EAST INDIAN-WEST PACIFIC

The SST anomalies in the East Indian and West Pacific continue their lagged rise in response to the El Nino. Will they also rise, noticeably, in response to the La Nina as they have in the past?

I’ve added this dataset in an attempt to draw attention to the upward step response. Using the 1986/87/88 and 1997/98 El Nino events as references, East Indian-West Pacific SST Anomalies peak about 7 to 9 months after the peak of the NINO3.4 SST anomalies, so we shouldn’t expect any visible sign of a step change for almost 18 to 24 months. We’ll just have to watch and see.

22 comments:

John
said...

I wonder how much the S. Atlantic anomalies are due to the weak hurricane season last year.

Unless this El Nino persists long enough to keep the shearing winds high enough to disrupt the hurricane development like it did last year, I don't see how this will be anything but a strong season. Those are some strong anomalies right in the center of the hurricane breeding grounds.

Anonymous: You asked, “By the way, how are behaving the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation(AMO)?...And the Pacific Decadal Oscillation(PDO)?”

This post presents SST anomalies for ocean basins, not climate indexes. But since you asked… It’s still too early for the updated AMO and PDO values for March 2010, so you’d have to check the links in a few days.

The NAO for April 6 is positive:http://www.cpc.noaa.gov/products/precip/CWlink/pna/nao_index.html

The AMO is positive (February):http://www.esrl.noaa.gov/psd/data/correlation/amon.us.long.data

The PDO is positive (also a February value):http://jisao.washington.edu/pdo/PDO.latest

Thus, Strongly positive AMO means that Atlantic is warm, but it's cooling and strongly negative AMO menas that Atlantic is cool, but it's warming. Value around zero does not tell you what the direction is.

El Nino-like phenomenon on Atlantic is cooling it: warm water does not travel north and instead it's staying on equator and radiating to the space.

On Indian ocean, there is also El Nino-like phenomenon going on. That's why it's so warm currently.

Anonymous (April 18, 2010 9:40 AM): The rises and falls of the North Atlantic SST anomalies and in turn the AMO are dictated by many other factors besides the Atlantic El Nino-like events. Thermohaline Circulation (THC)/Atlantic Meridional Overturning Circulation (AMOC) are responsible for the multidecadal variations. Changes in atmospheric circulation, resulting from El Nino and La Nina events in the tropical Pacific, cause short-term variations in North Atlantic SST anomalies.

Also, there is an El Nino-like phenomenon in the tropical Atlantic. Refer to page 6 of Wang (2001) “Atlantic Climate Variability and Its Associated Atmospheric Circulation Cells”:http://www.aoml.noaa.gov/phod/docs/wang_jc02_2.pdf

The ATL3 region SST anomalies have not reached the 0.7 deg C threshold of an “Atlantic El Nino” discussed in Wang (2001):http://i41.tinypic.com/105umqd.png

You wrote, “Thus, Strongly positive AMO means that Atlantic is warm, but it's cooling and strongly negative AMO menas that Atlantic is cool, but it's warming. Value around zero does not tell you what the direction is.”

Keep in mind that the AMO is detrended North Atlantic SST anomalies… http://i44.tinypic.com/qpqyox.png…so this generalization is not correct.

You wrote, “El Nino-like phenomenon on Atlantic is cooling it: warm water does not travel north and instead it's staying on equator and radiating to the space.”

Ocean circulation carries warm tropical waters toward the poles and at high latitudes it is better radiated to space.

"The rises and falls of the North Atlantic SST anomalies and in turn the AMO are dictated by many other factors besides the Atlantic El Nino-like events. Thermohaline Circulation (THC)/Atlantic Meridional Overturning Circulation (AMOC) are responsible for the multidecadal variations. Changes in atmospheric circulation, resulting from El Nino and La Nina events in the tropical Pacific, cause short-term variations in North Atlantic SST anomalies."

Patterns of long-time behavior in those El Nino/La Nina events are main causes of those multidecadal variations.

3-year El Nino (and it's Atlantic cousing) in start of 1940s caused a significant drop in heat content. To me this situation looks very similar and my prediction is continuing El Nino for two more years.

Short transition between El Nino/La Nina state does not have similar effect. It just moves the water around and - if possible - enhances transition of warm water to higher latitudes.

"Also, there is an El Nino-like phenomenon in the tropical Atlantic."

Yes; that was my point in fact.

"Keep in mind that the AMO is detrended North Atlantic SST anomalies… "

I don't trust SST data from the start of 1900s. Thus I think the real SST data and AMO are closer to each other than you might think.

"Ocean circulation carries warm tropical waters toward the poles and at high latitudes it is better radiated to space."

While you are technically correct, remember that radiation is enhancer proportionally to the actual temperature. That's why the earth is warmer during El Nino.

Actual temperatures on high latitude sea is still quite low and thus, the radiation is stronger when the warm water stays on equator.

Please identify the coordinates of the area of the equatorial or tropical Atlantic you are using to identify the "El Nino-like or La Nina-like events" in the Atlantic. That way I can plot the SST amomaly data and confirm what you're discussing.

"Please identify the coordinates of the area of the equatorial or tropical Atlantic you are using to identify the "El Nino-like or La Nina-like events" in the Atlantic. That way I can plot the SST amomaly data and confirm what you're discussing."

Anonymous: The following are two comparison graphs of NINO3.4 SST anomalies versus the SST anomalies for the tropical North Atlantic coordinates you gave (0-20N, 50W-0). In the first, the NINO3.4 data is unadjusted. The year-to-year variations in the tropical North Atlantic are small by comparison. http://i39.tinypic.com/2wn44rr.png

Then if we scale the NINO3.4 data by multiplying it by a factor of 0.35, we can see that the major variations in the tropical North Atlantic follow the changes in NINO3.4 region, indicating those variations in the North Atlantic are aftereffects of the El Nino and La Nina events in the Pacific.http://i39.tinypic.com/11brjbp.png

"Then if we scale the NINO3.4 data by multiplying it by a factor of 0.35, we can see that the major variations in the tropical North Atlantic follow the changes in NINO3.4 region, indicating those variations in the North Atlantic are aftereffects of the El Nino and La Nina events in the Pacific."

You probably mean that they are effects of the same trade wind variations, which are the cause of El Nino/La Nina events?

Anonymous (April 22, 2010 2:29 PM): Refer to Wang (2005). That paper describes how sea surface temperatures can and do rise in response to El Nino events in areas of the global oceans remote to the tropical Pacific. It concentrates on the Tropical North Atlantic and the Western Hemisphere Warm Pool. Basically, the changes in sea surface temperature of the North Atlantic are responses to changes in atmospheric circulation caused by ENSO.http://www.aoml.noaa.gov/phod/docs/Wang_Hadley_Camera.pdf

"Basically, the changes in sea surface temperature of the North Atlantic are responses to changes in atmospheric circulation caused by ENSO."

I don't agree with Wang. North Atlantic temperature changes are mainly caused by variations of trade winds, which causes variation to the warm water flow from equator to north Atlantic.

Currently it is easy to see what is happening:http://weather.unisys.com/archive/sst/sst_anom-100418.gif

Observe the cold anomaly from Gulf of Mexico to northeast. This is result of lesser strength in trade winds causing "El Nino"-like effect on equator (and thus warming it) and cold sea in as seen in satellite picture in north.

Atmospheric circulation itself does not cause any noticeable changes to the sea temperatures at equator. Cause is the sun, which can warm the sea without wind moving the warm water to the north.

Enfield and Mayer 1997 has found the right reason for Atlantic equator temperature variations:http://europa.agu.org/?uri=/journals/jc/96JC03296.xml&view=article

Same is essentially described here (Wang et al 2005 http://www.aoml.noaa.gov/phod/docs/wang_etal_2005_jcl_submitted.pdf):

"As reviewed recently by Wang et al. (2004), a common feature of all three tropical oceans is for the Bjerknes’ positive ocean-atmosphere feedback to exist in all ocean basins. In the tropical Atlantic, the Bjerknes’ feedback mechanism results in the Atlantic Niño (Zebiak 1993) that is similar to the Pacific El Niño. The Atlantic Niños resemble their Pacific counterparts in that they involve the disappearance of the cold tongue of water along the equator (during the boreal summer), a surge of warm tropical water eastward and then southward along the southern coast of Africa, an anomalous reversal of direction of the equatorial trade winds, and shifts of atmospheric convection towards the anomalous warm water in the east. However,they are weaker and more frequent than the Pacific El Niños."

On the other hand this paper has the cause and the effect wrong:http://journals.ametsoc.org/doi/full/10.1175/1520-0442%282000%29013%3C2177%3AIBTAVA%3E2.0.CO%3B2

They even make a reference to the Enfield and Mayer paper above, but still don't even mention word "trade wind" in the paper.

This Alexander at al paper shows correlation picture (figure 2), which are exact match of current situation (http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282002%29015%3C2205%3ATABTIO%3E2.0.CO%3B2). See any current satellite picture and you can see the exactly the same as figure 2 shows on Atlantic currently.

All other "Teleconnection"-related text in that paper - however - is pure garbage.

ENSO is not the reason for Atlantic equator temperature changes; it's the trade winds.

You concluded your comment, “ENSO is not the reason for Atlantic equator temperature changes; it's the trade winds.”

The variations in the Pacific trade winds and the corresponding El Niño/La Niña can alter the trade winds in the Atlantic. The Pacific dominates and causes changes in atmospheric circulation globally, including the tropical Atlantic. Tropical Atlantic SST anomalies rise in response to the 1997/98 El Niño. http://i46.tinypic.com/25km0d1.gif

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